This invention relates generally to a structure for packaging together a light generating or detecting device, a lens and an optical fiber and more particularly to a packaging arrangement wherein light loss occurring between the lens and the optical fiber, which ordinarily is caused by an accumulation of dimension tolerances, is substantially reduced.
There are means in the art for packaging together a light device, such as an LED light source, a lens, and an optical fiber so that the light from the LED is focused through the lens onto the optical fiber or, alternatively, the light from the optical fiber is focused through the lens onto a light sensitive device. Such prior art packaging means involves the securing of the light device upon a header and then securing the header in a flange at one end of a metal sleeve with the lens being secured at the other end of the metal sleeve to form a lens package. This lens package is then secured in a first cavity in a plastic housing which also has a second cavity for retaining and securing the optical fiber.
The end of the optical fiber preferably is placed as close to the lens as possible and along the focal axis thereof so that efficient transmission of light between the lens and the optical fiber can occur. In such prior art structure, however, the position of the lens with respect to the fiber is determined by the length of the sleeve and the header dimensions since the header is secured in the flange formed at the first end of the sleeve. More specifically, the flange is secured in the plastic housing so that all tolerance errors between the flange and the end of the lens are cumulative. Such tolerance errors include not only the sleeve and header dimensions but also the shape and size of the lens. Such total cumulative error can be substantial and amount to a loss of as much as 4.0 or 4.5 decibels in the transmission of light between lens and fiber.